/*
 * V4L2 video capture example
 * AUTHOT : WANGTISHENG
 * DATA : 2013-12-18
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <getopt.h> /* getopt_long() */
#include <fcntl.h> /* low-level i/o */
#include <unistd.h>
#include <errno.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/mman.h>
#include <sys/ioctl.h>

#include <linux/videodev2.h>

#define CLEAR(x) memset(&(x), 0, sizeof(x))

struct buffer {
    void *start;
    size_t length;
};

static char *dev_name;
static int fd = -1;        //DEVICE NUMBER
struct buffer *buffers;
static unsigned int n_buffers;
static int frame_count = 100;
FILE *fp;                                //FILE POINTOR

static void errno_exit(const char *s)
{
    fprintf(stderr, "%s error %d, %s\n", s, errno,
            strerror(errno));
    exit(EXIT_FAILURE);
}

static int xioctl(int fh, int request, void *arg)
{
    int r;
    static int oooo = 0;
    do {
    	printf("%s ## %s ## %d  ## %d\n", __FILE__, __func__, __LINE__, oooo);
        r = ioctl(fh, request, arg);
        oooo++;

	} while (-1 == r && EINTR == errno);

    return r;
}
//处理函数
static void process_image(const void *p, int size)
{
    fwrite(p,size, 1, fp);
}

static int read_frame(FILE *fp)
{
    struct v4l2_buffer buf;

    CLEAR(buf);
    buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    buf.memory = V4L2_MEMORY_MMAP;
	printf("%s ## %s ## %d\n", __FILE__, __func__, __LINE__);
    if (-1 == xioctl(fd, VIDIOC_DQBUF, &buf))
	{
		printf("%s ## %s ## %d\n", __FILE__, __func__, __LINE__);
		errno_exit("VIDIOC_DQBUF");
	}
    process_image(buffers[buf.index].start, buf.bytesused);
    if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))
        errno_exit("VIDIOC_QBUF");

    return 1;
}

static void mainloop(void)
{
    unsigned int count;
    count = frame_count;
    while (count-- > 0) {
        printf("No.%d\n",frame_count - count);
        //显示当前帧数目
        read_frame(fp);
    }
    printf("\nREAD AND SAVE DONE!\n");
}

static void stop_capturing(void)
{
    enum v4l2_buf_type type;

    type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    if (-1 == xioctl(fd, VIDIOC_STREAMOFF, &type))
        errno_exit("VIDIOC_STREAMOFF");
}

static void start_capturing(void)
{
    unsigned int i;
    enum v4l2_buf_type type;

    for (i = 0; i < n_buffers; ++i) {
        struct v4l2_buffer buf;

        CLEAR(buf);
        buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        buf.memory = V4L2_MEMORY_MMAP;
        buf.index = i;

        if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))
            errno_exit("VIDIOC_QBUF");
    }
    type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    if (-1 == xioctl(fd, VIDIOC_STREAMON, &type))
        errno_exit("VIDIOC_STREAMON");
}

static void uninit_device(void)
{
    unsigned int i;

    for (i = 0; i < n_buffers; ++i)
        if (-1 == munmap(buffers[i].start,
                    buffers[i].length))
            errno_exit("munmap");

    free(buffers);
}

static void init_mmap(void)
{
    struct v4l2_requestbuffers req;

    CLEAR(req);

    req.count = 4;
    req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    req.memory = V4L2_MEMORY_MMAP;

    if (-1 == xioctl(fd, VIDIOC_REQBUFS, &req)) {
        if (EINVAL == errno) {
            fprintf(stderr, "%s does not support "
                    "memory mapping\n", dev_name);
            exit(EXIT_FAILURE);
        } else {
            errno_exit("VIDIOC_REQBUFS");
        }
    }

    if (req.count < 2) {
        fprintf(stderr, "Insufficient buffer memory on %s\n", dev_name);
        exit(EXIT_FAILURE);
    }

    buffers = calloc(req.count, sizeof(*buffers));

    if (!buffers) {
        fprintf(stderr, "Out of memory\n");
        exit(EXIT_FAILURE);
    }

    for (n_buffers = 0; n_buffers < req.count; ++n_buffers) {
        struct v4l2_buffer buf;

        CLEAR(buf);

        buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        buf.memory = V4L2_MEMORY_MMAP;
        buf.index = n_buffers;

        if (-1 == xioctl(fd, VIDIOC_QUERYBUF, &buf))
            errno_exit("VIDIOC_QUERYBUF");

        buffers[n_buffers].length = buf.length;
        buffers[n_buffers].start =
            mmap(NULL /* start anywhere */,
                    buf.length,
                    PROT_READ | PROT_WRITE /* required */,
                    MAP_SHARED /* recommended */,
                    fd, buf.m.offset);

        if (MAP_FAILED == buffers[n_buffers].start)
            errno_exit("mmap");
    }
}


static void init_device(void)
{
    struct v4l2_capability cap;
    struct v4l2_format fmt;

    if (-1 == xioctl(fd, VIDIOC_QUERYCAP, &cap)) {
        //测试参数
        if (EINVAL == errno) {
            fprintf(stderr, "%s is no V4L2 device\n", dev_name);
            exit(EXIT_FAILURE);
        } else {
            errno_exit("VIDIOC_QUERYCAP");
        }
    }

    if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) {
        fprintf(stderr, "%s is no video capture device\n",
                dev_name);
        exit(EXIT_FAILURE);
    }

    if (!(cap.capabilities & V4L2_CAP_STREAMING)) {
        fprintf(stderr, "%s does not support streaming i/o\n", dev_name);
        exit(EXIT_FAILURE);
    }


    CLEAR(fmt);
    fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    fmt.fmt.pix.width = 640;
    fmt.fmt.pix.height = 480;
    fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;
    fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;

    if (-1 == xioctl(fd, VIDIOC_S_FMT, &fmt))        //设置格式
        errno_exit("VIDIOC_S_FMT");
    init_mmap();
}

static void close_device(void)
{
    if (-1 == close(fd))
        errno_exit("close");

    fd = -1;
}

static void open_device(void)
{
    //加上O_NONBLOCK会出现如下错误
    //VIDIOC_DQBUF error 11, Resource temporarily unavailable
    fd = open(dev_name, O_RDWR  /* required | O_NONBLOCK */,
            0);

    if (-1 == fd) {
        fprintf(stderr, "Cannot open '%s': %d, %s\n",
                dev_name, errno, strerror(errno));
        exit(EXIT_FAILURE);
    }
}

int main(int argc, char **argv)
{
    dev_name = "/dev/video0";

    if ((fp = fopen("test.yuy2", "w")) == NULL) {
        perror("Creat file failed");
        exit(0);
    }
    open_device();
    init_device();
    start_capturing();
    mainloop();                //主要处理均在该函数中实现
    fclose(fp);
    stop_capturing();
    uninit_device();
    close_device();
    //fprintf(stderr, "\n");
    return 0;
}
